Developmental expression of interstitial collagen genes in fetal bladders

Bovine bladders at 3 stages during fetal development were examined for expression of collagens by immunohistochemistry as well as by measurement of steady state mRNA levels. Expression of type I and type III collagens during the fetal period was compared with that of adult cows as well as a young animal (heifer). Each bladder was separated into a detrusor and a urothelial-lamina propria sample which were then analyzed separately. Distribution and fiber arrangement of types I and III collagens were different depending upon the region of the bladder wall examined. Type III collagen, in particular, has a ''coiled'' appearance which is especially prominent within the lamina propria. Collagen gene expression showed a distinctive pattern which was different for both type I and type III collagen. While type I collagen gene expression peaked during the late second to early third trimester, type III collagen expression progressively decreased throughout the fetal period. In addition, expression of both collagens was greater in the urothelial-lamina propria fractions. These data demonstrate that the pattern of collagen gene expression in the developing bladder is developmentally regulated and is unique to each of the two major structural layers.